Gyroscopes are currently used in a number of military and civilian applications. One common application involves using gyroscopes, known as control moment gyroscopes (CMGs), to control the attitude (or orientation) of a spacecraft, satellite, or another agile vehicle. A CMG comprises a spinning rotor and one or more motorized gimbals, which are used to rotate the axis of rotation of the rotor (e.g., gimballing), which in turn alters the direction of the angular momentum vector of the rotor. This change in angular momentum produces a reactionary torque which causes the spacecraft to rotate to the desired attitude or orientation. Attitude control systems (ACSs) and other spacecraft orienting applications often utilize a momentum control system (MCS) that includes at least three CMGs, also known as a CMG array.
During operation of the agile vehicle, it may be desirable to cease rotation or otherwise reduce angular velocity of the agile vehicle. For example, in response to an interruption or loss of communication between an ACS and the MCS, ceasing rotation of the agile vehicle can prevent the agile vehicle from being oriented at an undesirable attitude. One way to reduce angular velocity and cease rotation of an agile vehicle involves locking the gimbals of the CMGs and utilizing other actuators onboard the agile vehicle to stop the agile vehicle's rotation. However, this approach depletes resources onboard the agile vehicle (e.g., fuel or electrical power) and may also suffer from a relatively long response time. Another approach involves unlocking the gimbals of the CMGs and allowing them to rotate freely. Angular momentum from the agile vehicle is absorbed by the CMG array until the angular velocity of the agile vehicle reaches zero, or the CMG array saturates. However, this approach requires gimbal motors that are capable of being backdriven.